title: CYP450 phenotyping and metabolite identification of quinine by accurate mass UPLC-MS analysis: a possible metabolic link to blackwater fever.
abstract: BACKGROUND
  The naturally occurring alkaloid drug, quinine is commonly used for the treatment of severe malaria. Despite centuries of use, its metabolism is still not fully understood, and may play a role in the haemolytic disorders associated with the drug.
  
  
  METHODS
  Incubations of quinine with CYPs 1A2, 2C9, 2C19, 2D6, and 3A4 were conducted, and the metabolites were characterized by accurate mass UPLC-MS(E) analysis. Reactive oxygen species generation was also measured in human erythrocytes incubated in the presence of quinine with and without microsomes.
  
  
  RESULTS
  The metabolites 3-hydroxyquinine, 2'-oxoquininone, and O-desmethylquinine were observed after incubation with CYPs 3A4 (3-hydroxyquinine and 2'-oxoquininone) and 2D6 (O-desmethylquinine). In addition, multiple hydroxylations were observed both on the quinoline core and the quinuclidine ring system. Of the five primary abundance CYPs tested, 3A4, 2D6, 2C9, and 2C19 all demonstrated activity toward quinine, while 1A2 did not. Further, quinine produced robust dose-dependent oxidative stress in human erythrocytes in the presence of microsomes.
  
  
  CONCLUSIONS
  Taken in context, these data suggest a CYP-mediated link between quinine metabolism and the poorly understood haemolytic condition known as blackwater fever, often associated with quinine ingestion.
authors.affiliation: Department of Drug Development, Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Marcsisin
authors.forename: Xiannu
authors.initials: X
authors.lastname: Jin
authors.forename: Theresa
authors.initials: T
authors.lastname: Bettger
authors.forename: Nicholas
authors.initials: N
authors.lastname: McCulley
authors.forename: Jason C
authors.initials: JC
authors.lastname: Sousa
authors.forename: G Dennis
authors.initials: GD
authors.lastname: Shanks
authors.forename: Babu L
authors.initials: BL
authors.lastname: Tekwani
authors.forename: Rajnish
authors.initials: R
authors.lastname: Sahu
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Reichard
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sciotti
authors.forename: Victor
authors.initials: V
authors.lastname: Melendez
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Pybus
mesh_terms: D001742:Blackwater Fever / Q000209:etiology*; D002853:Chromatography, Liquid; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004912:Erythrocytes / Q000187:drug effects; D006801:Humans; D008288:Malaria / Q000150:complications* / Q000188:drug therapy*; D013058:Mass Spectrometry; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D011803:Quinine / Q000009:adverse effects* / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000032:analysis
chemical_list: D017382:Reactive Oxygen Species; D003577:Cytochrome P-450 Enzyme System; D011803:Quinine